1. Field of the Invention
This invention relates to a method and means for exhausting processing gases inside a dry etching apparatus, and more particularly, to a dry etching apparatus having a wafer chuck equipped with an exhausting means.
2. Description of the Prior Art
Vertical dry etching techniques are widely used in defining a semiconductor device of sub-micron features. Most of the dry etching techniques for semiconductor integrated circuit devices use processing gases introduced into a vacuum processing chamber at a low pressure. A high-frequency power is applied to convert the processing gases into a gas plasma. A workpiece such as a semiconductor wafer to be processed is affixed to a wafer chuck, being subject to an etching process. The gas plasma is then exhausted by an exhaust means located at lower side portions of the vacuum processing chamber.
In the etching process, non-uniform etching would produce an adverse effect on the wafers. This non-uniform etching phenomenon is influenced by various factors such as high frequency electric field, flow of the processing gases and the concentration of etching gas in the processing chamber. In the case of plasma etching, since the processing is carried out by utilizing a chemical reaction, dust particles, for example, reaction product, are produced during the processing, and such dust particles are deposited on the semiconductor wafer and the inner wall of the processing chamber in the plasma processing apparatus. It is known in the art that this causes various problems, and that the use of an electrostatic chuck can reduce the particle contamination problem. Examples of typical electrostatic chuck are Abe U.S. Pat. No. 4,384,918 and Collins et al. U.S. Pat. No. 5,350,479, both of which are incorporated herein for reference. Still, it is inevitable that small particles are formed. The particles cause yield problems and required frequent cleaning of the processing chamber.
It is, therefore, an object of this invention to provide a new method and means for exhausting the processing gases from the processing chamber in a dry etching apparatus.
It is another object of this invention to provide a method and means for applying an uniform gas plasma to the wafer to be processed on the wafer chuck.
It is yet another object of this invention to provide a method for reducing particles of the etching gas that remains on the semiconductor workpiece in a dry etching apparatus.
It is a further object of this invention to provide a method for avoiding frequent cleaning of the vacuum processing chamber in a dry etching apparatus.
According to this invention, a new method for exhausting processing gases from a dry etching apparatus, comprising the steps of: introducing the processing gases into the processing chamber, plasma etching the semiconductor workpiece to be processed, centrally gathering gas plasma into the space below the semiconductor workpiece by sucking force formed around the bottom periphery of the semiconductor device, and exhausting the gas from the dry etching apparatus.